SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '553f5f84935908a718644a72965ad40cda81eec381353033633bc2bd1613c4af' 
  AND token = 'e11Vgze2OAzKGg9VnhQXGKV5wKdsJ5XxHXlvBIWv2M8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}